File:STL Skyline 2007 edit cropped.jpg|thumb|The Gateway Arch in St. Louis. One of many notable structures built by the Pittsburgh-Des Moines Steel Co.
File:City of Cotton Plant.jpg|thumb|Cotton Plant Water Tower in Arkansas, built 1935 by the Pittsburgh-Des Moines Steel Co.
The '''Pittsburgh-Des Moines Steel Company''' (originally the '''Des Moines Bridge and Iron Company'''), and often referred to as '''Pitt-Des Moines Steel''' or '''PDM''' was an American steel fabrication company. It operated from 1892 until approximately 2002 when its assets were sold to other companies, including Chicago Bridge & Iron Company
The company began as a builder of steel water tanks and bridges. It also later fabricated the "forked" columns for the World Trade Center (1973–2001)|World Trade Center in the 1960s, [[http://www.lukenshistoricdistrict.org/treespdm.htm Lukens Historic District -... ]